The invention concerns the cleaning of material jet heads as well as the machines and manufacturing equipment equipped with self-cleaning material jet heads.
“Material jet heads” means here both tinctorial inkjet printing heads and heads for spraying liquids or viscous or powdery products.
In addition, the fields to which the invention applies relate, beyond tinctorial printing with inks, the material jet having medical, biological, genetic, chemical, acoustic, insulating or electrically conductive functions or properties, or the like.
For example, the document WO-A-9919900 shows various uses of the material jet, apart from printing.
The devices employing material jet heads are used for spraying drops of material on a substrate so as to form an image or a three-dimensional structure.
The document FR-A-2790421, filed in the name of the applicant, describes a graphical material jet machine provided with at least one inkjet head.
This document supplies an example of the use of material jet heads for printing patterns on a support such as a chip card.
The document U.S. Pat. No. 5,449,754 describes a method of producing chemical compounds by spraying drops of various liquid solutions onto a substrate.
This document supplies an example of the use of material jet heads for an application in chemistry.
The methods and devices for spraying droplets of material have the characteristic of being sensitive to clogging of the material outlet orifices.
This is because these orifices have a diameter of around a few tens of microns and because of this the least impurity may interfere with the jet of material.
In addition, because of their function of spraying material, these orifices are highly susceptible to being blocked by residues of dry material after use.
Periodic cleaning devices for material jet heads have therefore been developed.
In particular, it is known how to provide a purge phase during which a large quantity of material is expelled through the outlet orifices, a receptacle also being provided to collect the purged material.
This solution has a certain number of drawbacks, including the difficulty of making the receptacle/orifices assembly liquidtight, the receptacle being removable. Moreover, the risk of running is significant in the case of a material jet head which can take various positions.
It is also known how to provide a rubber scraper able to scrape the material outlet orifices during a cleaning phase so as to remove the residual drops of material.
This type of device does not currently give satisfaction because of the difficulty in recovering the scraped material and the need for periodic cleaning of the scraper itself.
It is also known how to provide phases of cleaning the material jet heads by disposing a ribbon under the material jet head, pressing it against the material outlet orifices by means of a pad; and then causing it to move so as to wipe these orifices.
This solution, although more satisfactory than the previous ones, does not leave a sufficiently clean surface state for a quality material jet.